This invention relates in general to evaporation and distillation apparatus of the wobble-tube type described in U.S. Pat. No. 4,230,529. More specifically, it relates to an improved evaporator or distillation apparatus of this type which also has a whip rod that spreads the incoming fluid stream into a very thin, even film.
Known apparatus for evaporation or distillation can be used for concentration by removing part of the liquid (as in orange juice), for desalination by condensing the water vapor, or for distillation by separating the various ingredients in the fluid (as in alcohol and water). In all these applications the evaporation (or condensation) of the fluid occurs primarily at the interface between the liquid and its vapor while the needed energy is transmitted from a heat source through the container wall to the liquid and then through the liquid to the interface to support the evaporation.
While the basic concept of distillation of sea water or other fluids, with or without vapor compression, is not new, conventional distillation systems such as multiple stage flash (MSF) systems require a substantial energy input to heat fluids and drive compressors. Additionally there is a substantial temperature gradient per stage which limits the number of usable stages with a given temperature rise or energy input. This correspondingly limits the output. Further, MSF equipment has a high capital cost.
"Falling film" systems are also known where fine spray nozzles produce a downwardly falling thin film of fluid on the side of a vertical or horizontal tube that is stationary. Falling film systems have reduced capital costs and operate more efficiently than MSF systems. However, they have not proven to be reliable. One problem is that the fluid is applied to a heat transfer surface by a number of small nozzles that often malfunction. Also, there is no positive way to assure an even distribution of the thin film and there is a problem in cleaning the scale deposited on the tube by the evaporation.
It is an object of the present invention to reduce the power required and accordingly reduce the operating cost of an evaporation or distillation apparatus.
A further object is to lower the heat resistance of the fluid film being evaporated and reduce temperature differentials.
Another object is to provide a positive mechanical distribution of the fluid into an even, highly thin film without interfering with the introduction of the fluid to the tube.
Still another object is to control the build up of scale or other residue left by the evaporation process on the heat transfer surface.
A further object is to provide a mechanical distribution system with the foregoing advantages that can also serve as a component of a fluid distribution system.
Another object is to provide an evaporation or distillation system with the foregoing advantages that is mechanically simple, has a low cost, is highly reliable, and has a comparatively long operating life.